The present invention relates to catheters, and more particularly to balloon and tip assemblies for such catheters.
In the past, a various assortment of catheters, such as Foley catheters and endotracheal tubes, have been proposed for use in patients. In the case of urinary catheters, a conventional Foley catheter is normally constructed having a shaft defining a drainage lumen extending from a drainage eye adjacent a distal end of the catheter and an inflation lumen in a wall of the shaft, and having an expansible balloon overlying a distal portion of the shaft and defining a cavity communicating with the inflation lumen. In use, the distal end of the catheter is passed through the urethra until the drainage eye and balloon are located in the patient's bladder, and the balloon is inflated in the bladder to retain the catheter in the patient with a proximal end of the catheter located outside the patient's body. During catheterization, urine passes from the bladder through the drainage eye and lumen, and from the catheter through a drainage tube to a bag for collection therein.
A great majority of Foley catheters have been made from latex rubber through dipping techniques known to the art. However, a number of problems have been encountered with conventional latex catheters, particularly delamination of the catheter shaft causing blockage in the inflation lumen. Accordingly, there has been a desire to construct catheters from materials which display superior properties both from the view of improved performance during use and permitting simplified manufacture to reduce cost. For example, it is preferred that the catheter shaft be made from a material which can be extruded in order to facilitate the manufacturing process and eliminate the delamination problems in the shaft associated with dipped latex catheters. Additionally, the materials of the catheter shaft must be compatible with the patient's body to prevent deleterious results during use. The shaft, although flexible, should also have sufficient rigidity to permit placement of the catheter and prevent collapse of the shaft side walls. The balloon, of course, should be flexible and elastic to permit inflation in the patient's bladder, and preferably has a sufficient memory to assume its initial deflated configuration against the catheter shaft while being removed from the patient.
Unfortunately, many of the materials which display excellent properties when used for the catheter shaft are not suitable as a balloon, and vice versa. Hence, in many cases it is necessary to use dissimilar materials for the balloon and shaft which has created serious difficulties in joining the balloon and shaft together. Although it is often relatively simple to obtain a satisfactory bond between the balloon and shaft when the same material is used for both, known bonding techniques such as adhesive or heat sealing often do not provide sufficient strength between the balloon and shaft when dissimilar materials are used. For example, porous polytetrafluoroethylene provides an excellent candidate for the catheter shaft, but has been found unsatisfactory as the catheter balloon. Accordingly, attempts have been made to bond balloons made of suitable materials, such as silicone and latex, to such a shaft, and satisfactory bonds are only obtained with extreme difficulty which unduly complicates manufacture of the catheters.